Study on the Adsorption of Cr3+ by Peanut Shell: Adsorption Kinetics, Thermodynamics, and Isotherm Properties.

The pollution of heavy metals in soil to the environment is becoming more and more serious, resulting in the reduction of crop production and the occurrence of medical accidents. In order to remove heavy metal ions from soil and reduce the harm of heavy metals to the environment, modified peanut shell was used to adsorb Cr3+ in this article. The effects of different adsorption conditions on the adsorption rate and adsorption capacity of Cr3+ on ZnCl2 modified peanut shell were studied, the best adsorption conditions were explored, and the relationship of kinetics, thermodynamics and adsorption isotherm properties of adsorption process were explored. The results showed that the optimum adsorption pH value, dosage, initial concentration, adsorption temperature and contact time of ZnCl2 modified peanut shell were 2.5, 2.5 g/L, 75 µg/mL, 25 °C and 40 min, respectively. The prepared materials were characterized and analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD) analyzer. It was concluded that the modified peanut shell had a good adsorption capacity to Cr3+ . The kinetic study showed that the adsorption process of Cr3+ on peanut shell modified by zinc chloride was in accordance with the quasi-second-order kinetic model. The adsorption process belonged to exothermic reaction and belonged to spontaneous reaction process. In summary, it is proved that zinc chloride modified peanut shell can efficiently adsorb Cr3+ , which can be used for the treatment of heavy metal wastes in industry, which is beneficial to environmental protection and avoid heavy metal pollution.

Studies of adsorption of crystal violet from aqueous solution by nano mesocellular foam silica: process equilibrium, kinetic, isotherm, and thermodynamic studies.

Mesocellular foam (MCF) silica molecular sieve material was successfully synthesized using a hydrothermal method. X-ray diffraction, infrared spectroscopy, low nitrogen adsorption-desorption, scanning electron microscopy, and transmission electron microscopy (TEM) characterization techniques were used to characterize the material. Low temperature nitrogen adsorption-desorption method showed that pore size of the synthesized MCF was 12 nm. TEM study showed that the synthesized MCFs had honeycomb structure pores, which can be good for the absorbance of dye organic macromolecule substances. This work studied the adsorption of crystal violet by MCF and the results showed that when the adsorptive conditions were pH = 9.0, MCF:crystal violet = 150:1, and when the contact time was 10 min at room temperature of 25 ± 1 °C, the adsorption rate reached 99.71% and adsorption capacity was 6.646 mg/g. This study found that the adsorption is a Freundlich type, it is a multimolecular layer adsorption, and it belongs to the pseudo-second-order kinetic model. According to the ΔG0 obtained from adsorption thermodynamics, when the temperature is 25-40 °C, the adsorption enthalpy change ΔH0 = -25.65 kJ/mol, ΔG0 < 0, the adsorption is an exothermic reaction and can spontaneously occur. The adsorption entropy change ΔS0 = 5.54 J/(mol·K) and the entropy of system increased.

Preparation and controlled release of mesoporous MCM-41/propranolol hydrochloride composite drug.

This article used MCM-41 as a carrier for the assembly of propranolol hydrochloride by the impregnation method. By means of chemical analysis, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and low-temperature N(2) adsorption-desorption at 77 K, the characterization was made for the prepared materials. The propranolol hydrochloride guest assembly capacity was 316.20 ± 0.31 mg/g (drug/MCM-41). Powder XRD test results indicated that during the process of incorporation, the frameworks of the MCM-41 were not destroyed and the crystalline degrees of the host-guest nanocomposite materials prepared still remained highly ordered. Characterization by SEM and TEM showed that the composite material presented spherical particle and the average particle size of composite material was 186 nm. FT-IR spectra showed that the MCM-41 framework existed well in the (MCM-41)-propranolol hydrochloride composite. Low-temperature nitrogen adsorption-desorption results at 77 K showed that the guest partially occupied the channels of the molecular sieves. Results of the release of the prepared composite drug in simulated body fluid indicated that the drug can release up to 32 h and its maximum released amount was 99.20 ± 0.11%. In the simulated gastric juice release pattern of drug, the maximum time for the drug release was discovered to be 6 h and the maximum cumulative released amount of propranolol hydrochloride was 45.13 ± 0.23%. The drug sustained-release time was 10 h in simulated intestinal fluid and the maximum cumulative released amount was 62.05 ± 0.13%. The prepared MCM-41 is a well-controlled drug delivery carrier.

Determination of trace amount of oxalic acid with zirconium(IV)-(DBS-arsenazo) by spectrophotometry.

A novel method is proposed for the determination of trace amount of oxalic acid in the present article. In 1.0M hydrochloric acid medium, oxalic acid can react with the zirconium(IV) in Zr(IV)-(DBS-arsenazo) complex and replaces the DBS-arsenazo to produce a hyperchromic effect at 520 nm. The hyperchromic degree is proportional to the concentration of the oxalic acid added over a defined range. Based on this property, a new method for the spectrophotometric determination of trace oxalic acid was developed. Beer's law is held over the concentration range of 9.0 x 10(-6) to 5.0 x 10(-4)M for oxalic acid with a correlation coefficient of 0.9995. The apparent molar absorptivity of the method is epsilon520 nm = 1.16 x 10(3)L mol(-1)cm(-1) and the detection limit for oxalic acid is 0.815 microg/mL. The developed method was directly applied to the determination of oxalic acid in tomato samples with satisfactory results.

Kinetic-spectrophotometric determination of trace amounts of vanadium(V) based on its catalytic effect on the reaction of DBM-arsenazo and potassium bromate.

A simple and sensitive kinetic-spectrophotometric method is developed for the determination of trace vanadium(V), based on the catalytic effect of vanadium(V) on the oxidation of DBM-arsenazo by potassium bromate in 0.0138 moll(-1) phosphoric acid medium and at 100 degrees C in the presence of citric acid as activator. The absorbance is measured at 528 nm with the fixed-time method. The optimization of the operating conditions regarding concentrations of the reagents, temperature and interferences are also investigated. The working curve is linear over the concentration range 0-20 ngml(-1) of vanadium(V) with good precision and accuracy and the detection limit was down to 3.44 ngl(-1). The relative standard deviation for a standard solution of 14 ngml(-1) is 0.28% (n=11). The apparent activity energies of the catalytic reaction and the non-catalytic reaction are 73.48, 113.5 kJ/mol, respectively. The proposed method proved highly sensitive, selective and relatively rapid for the assay of vanadium at low-level range of 0-20 ngml(-1) without any pre-concentration step. Thw method was applied to the determination of vanadium(V) in steels, rice, flour, cabbage, potato, fish, shrimp and tea samples with satisfactory results. The obtained results for the steel samples were excellent agreement with the standard reference values. The analytical results of the rice, flour, cabbage, potato, fish, shrimp and tea samples were excellent agreement with those of atomic absorption spectrometry. The recovery experiments have been made for the rice, flour, cabbage, potato, fish, shrimp and tea samples except the steels; excellent results were obtained. The relative standard deviations were over the range of 0.18-2.60% and the recoveries were over the range of 98.00-102.4%, respectively. The analytical results obtained were satisfactory.

Catalytic kinetic spectrophotometry for the determination of trace amount of oxalic acid in biological samples with oxalic acid-rhodamine B-potassium dichromate system.

A new catalytic kinetic spectrophotometric method was proposed for determining trace oxalic acid based on the catalytic effect of oxalate on the oxidation of potassium dichromate with rhodamin B in 0.10 M of sulfuric acid. Good linearity is obtained over the concentration range 0.40-6.0 microg/mL of oxalic acid. After the reactions of the catalytic and non-catalytic systems were terminated by using 2.00 mL of 4 M sodium hydroxide solution, they can be stable for 3 h at room temperature. The apparent activation energy of the catalytic reaction is 12.44 kJ/mol. The effect of 50 coexisting substances was observed. The method was used to determine trace oxalic acid in tea, spinach and urine samples with satisfactory results.